1. Field of the Invention
The present invention relates to a position indicator and a manufacturing method thereof and particularly to a position indicator used in a touch input system and a manufacturing method thereof.
2. Description of the Related Art
Among touch input systems composed of a position detecting device that is a plate-shaped input unit and a position indicator such as an electronic pen are ones that are configured so that the position indicator is capable of transmitting various kinds of information toward the position detecting device and the power necessary for the transmission is supplied from the position detecting device to the position indicator. The position indicator used in this kind of input system is provided with an LC resonant circuit composed of a coil excited by a magnetic field from a sensor coil of the position detecting device and a capacitor connected in parallel to this coil (refer to e.g. Japanese Patent Laid-open No. 2014-130394). When this LC resonant circuit enters the magnetic field, an induced electromotive force is generated in the coil, whereby power is stored in the LC resonant circuit. The position indicator transmits pen information including writing pressure information, side switch information, and so forth by using this power.
In order for the position detecting device to correctly receive the information transmitted by the position indicator, the resonant frequency of the LC resonant circuit needs to be equal to a standard value prescribed in advance. However, errors in manufacturing are caused in the inductance of the coil and the capacitance of the capacitor. Therefore, the occurrence of variation in the resonant frequency is inevitable at the stage immediately after assembling of the LC resonant circuit. Then, the following processing is carried out in a step for manufacturing the position indicator. Specifically, plural capacitors are disposed in parallel to each other in advance. The resonant frequency is measured after the LC resonant circuit is assembled and several capacitors are isolated from the circuit by cutting interconnects according to the measurement result. Thus, the resonant frequency is adjusted to the standard value in an ex-post manner.
However, this cutting of interconnects is performed by manual work thus far and therefore the work cost is high and an improvement is demanded. It will be possible to replace part or all of the plural capacitors by a trimmer capacitor, whose capacitance can be adjusted. However, the trimmer capacitor has other problems that it is impossible to ensure a large adjustment width, that the element itself is expensive, and so forth.
As one of methods to reduce the work cost taken for the interconnect cutting, a method of cutting interconnects not by manual work but by a laser will be possible. Using a laser can automate the interconnect cutting work and thus can reduce the work cost. However, a laser with some degree of intensity needs to be used to surely cut the interconnect and the interconnect cutting by use of such a laser causes a new problem that a large hollow region is generated in a substrate around the interconnect. In particular, in the case of the substrate used in the position indicator, the thickness of the substrate is very thin, about 0.35 mm, and therefore the hollow region penetrates to the back surface of the substrate and even an interconnect on the back surface is cut in some cases. Therefore, it is impossible to perform the interconnect cutting by a laser thus far.